1. Field of the Invention
The present invention is directed to helicopter rotor speed controls. More specifically, the present invention is directed to automatic dual rotor speed controls, which automatically transition between a high rotor speed and a lower rotor speed based upon received flight information.
2. Description of Related Art
Many helicopters include a main rotor and a tail rotor that are integrally connected together and driven by one or more engines. One known method for reducing a helicopter's noise level is to reduce the speed of the main and tail rotors. That is, it is known in the art to design a helicopter with a system, which incorporates a variable speed that enables the pilot to manually vary the speed of the main and tail rotors from a normal mode (e.g., high rotor speed) to a quiet mode (e.g., low rotor speed). More specifically, it is known, to design a helicopter with a pilot control system wherein when the pilot manually activates/deactivates the system so that the helicopter's flight control system reduces/increases the speed of the main and tail rotors so that the helicopter's noise levels are reduced/increased. To varying degrees and purposes, changing rotor speed has been automated, in particular based on density altitude and/or airspeed.
Future helicopters will strive to satisfy the Federal Aviation Administration (FAA) noise level requirements for the Quiet Aircraft Technology Designation (QATD). Accordingly, there is a continuing desire for helicopters and flight control systems that are capable of operating at lower noise levels.